Abstract:

Aqueous polyurethane (PU) prepolymers were synthesized by emulsion polymerization in situ , with toluene diisocyanate (TDI-80) , polyether binary alcohol (N21O) , dimethylol propionic acid (DMPA) , hydroxyl ethyl methacrylate (HEMA) , adipic dihydrazide (ADH) and diacetone acrylamide (DAAM) as the materials.Three kinds of aqueous polyurethane-acrylate (PUA) hybrid emulsions marked as PUA-l (free cross-linking) ,PUA-2 (synthesized cross-linking) and PUA-3 (cross-linking at ambient temperature) were synthesized after the free radical polymerization by adding initiator , which were then used to prepare three kinds of vamishes. The effects of the dosages of DMPA , HEMA , ADH and DAAM on the properties of emulsions and films were finally investigated.It is found that , when the mass fraction of -COOHin DMPA and the mass fractions of HEMA , ADH and DAAM in PU are respectively 2.5% , 1. 44% , 3.5% and 2.0% - 3. 0% , the emulsions and films are all of good properties. Moreover , the results obtained by particle size analyzer and TEM show that (1) the average particle sizes of PUA-l , PUA-2 and PUA-3 are respectively 40 - 50 nm,90 - 100 nm and 30 - 40 nm; (2) PU A-l particles are regular sphericities in shape , while PUA-2 particles are irregular sphericitis with interpenetrating polymer network between the core and the shell; (3) as compared with PUA-l , PUA-2 is oflarger particle size and wider particle size distribution; (4) PUA -3 is of very irregular particle shape , uniform particle size distribution and disorganized interpenetrating network between the shell and the core. Furthermore , in the three kinds of vanishes ,
the one prepared from PUA-3 is of the best water resistance , dry-heat resistance and stain resistance but is of the longest drying time for the film.

Key words: polyurethane, acrylate, emulsion, vamish, synthesis, property